In a conventional sewing machine, to meet sewing requirements, processes of sewing forward or sewing in reverse are frequently performed. Such processes are also commonly known as forward stitch and backstitch. The above sewing machine generally uses a single power source for controlling the change of direction of a structure to meet the requirements of forward stitch and backstitch. In a conventional backstitch transmission mechanism, a lever is manually moved to actuate a transmission element, a cloth feeding teeth member is driven by rotation of a transmission shaft, and a fabric is then forwarded or reversed by a rough surface of the cloth feeding teeth member, so as to backstitch the fabric. However, the above operation not only is time consuming, an operator also needs to constantly press the lever. As such, the operator may be further burdened in a way that work efficiency of the operator is lowered to fail in meeting economical considerations.
Therefore, the technique of incorporating connecting rods with an electromagnet is proposed for driving the backstitch transmission mechanism to achieve automatic backstitch. In the above structure, a plurality of connecting rods are coupled with and driven by the electromagnet, and the transmission element is controlled by the connecting rods. Although automatic backstitch is achieved through controlling the connecting rods with the electromagnet, such mechanism for controlling the cloth feeding teeth member to perform forward stitch and backstitch is rather complicated. Further, due to loosening or poor assembly of the connecting rods between the electromagnet and the transmission element, incorrect transmission may be generated. In addition, the above indirect driving mechanism through the connecting rods and the electromagnet is incapable of precisely controlling a rotation angle of the transmission element, such that precise movement of the cloth feeding teeth member may not be controlled precisely neither.